<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			div{
				width: 0px;/*宽高设置为0*/
				height: 0px;
				border-width: 10px;/*边框宽度设置宽些*/
				border-style: solid;/*实线*/
				border-color: transparent red transparent transparent; /*四边只留一边有颜色,其他设为透明*/
			}
		</style>
	</head>
	<body>
		<div></div>
	</body>
</html>
